1. Field of the Invention
The invention relates generally to a method of manufacturing a semiconductor device, and more particularly to, a method of manufacturing a semiconductor device in which a facet phenomenon generated by a selective epitaxial growth (called SEG hereinafter) used in forming a Lightly Doped Drain (LDD) structure and an elevated source/drain structure of a semiconductor device is used, thus obtaining a junction region having a very shallow depth.
2. Description of the Prior Art
As a semiconductor device is highly integrated, the depth of a device junction becomes also shallow. Thus, in order to shallow the depth of the junction region, a method of lowering the amount of the energy when ion injection process is applied, is used. However, this method has the following problems that it could not obtain a sufficient beam current upon ion injection and it will increase the possibility of channeling in a low ion injection energy etc.
In order to solve these problems, a SEG method has been proposed, by which a gate electrode is formed on a semiconductor substrate and then a silicon layer is selectively formed only on source and drain regions so as to increase the height of the source and drain regions.
FIG. 1 is a sectional view of a device for illustrating a method of manufacturing a conventional semiconductor device.
First a semiconductor device 11 is thermally oxidized to form a gate oxide film 12. Then a conductive layer 13 for use in a gate electrode and a first insulating film 14 are sequentially formed on the entire structure. Thereafter, a portion in which the gate electrode will be formed is defined by photolithography process and etching process. Then the first insulating film 14 and the conductive layer 13 are sequentially removed to form a gate electrode. Next, a LDD region 16 is formed by means of ion injection process using a low concentration impurity. Then, after forming a second insulating film 15 on the entire structure a blanket etching is performed to form spacers on both sides of the gate electrode. Thereafter, in order to form an elevated source/drain structure, a SEG process is performed to form a SEG layer 17. Finally, a high concentration ion injection process is performed to form a junction region 18.
In case of the method of forming a LDD structure of a semiconductor device as explained above as SEG process is performed after ion injection process for forming the LDD region 16 is performed, it could not solve the above mentioned problems that it could not obtain a sufficient beam current upon ion injection process and that it may increase the possibility of channeling in a low energy. Further, due to inherent SEG process, there are problems that a facet phenomenon (marked A) is occurred at the edge portion of the gate electrode and that the depth of junction is partially deepened (marked 13) at the place (marked A) where the facet phenomenon was occurred upon ion injection process for forming a subsequent junction regions 18. As the facet phenomenon occurs at the edge portion of the gate electrode, it is difficult to form a LDD structure in which the junction depth at the edge portion of the gate electrode is shallow and that at the other region of the gate electrode is deep.